package com.jlcloud.sequence;

import lombok.extern.slf4j.Slf4j;
import org.springframework.util.StringUtils;

import java.lang.management.ManagementFactory;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.concurrent.ThreadLocalRandom;

/**
 * 分布式高效有序ID生产黑科技(sequence)
 * <p>优化开源项目：https://gitee.com/yu120/sequence</p>
 *
 * @author By: zhangchunyang <br>
 * @Package: com.jlcloud.sequence <br>
 * @CreateTime: 2024-12-05 15:27 <br>
 * @Copyright: 2021 www.jilianjituan.com Inc. All rights reserved. <br>
 * @Caution 注意：本内容仅限于冀联人力集团内部传阅，禁止外泄以及用于其他的商业目的 <br>
 */
@Slf4j
public class Sequence {
	private static final String AT = "@";
	/**
	 * 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
	 * 下面时间为：2024-09-23 15:55:20
	 */
	private final long twepoch = 1288834974657L;
	/**
	 * 机器标识位数
	 */
	private final long workerIdBits = 5L;
	private final long datacenterIdBits = 5L;
	private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
	private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
	/**
	 * 毫秒内自增位
	 */
	private final long sequenceBits = 12L;
	private final long workerIdShift = sequenceBits;
	private final long datacenterIdShift = sequenceBits + workerIdBits;
	/**
	 * 时间戳左移动位
	 */
	private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
	private final long sequenceMask = -1L ^ (-1L << sequenceBits);

	private final long workerId;

	/**
	 * 数据标识 ID 部分
	 */
	private final long datacenterId;
	/**
	 * 并发控制
	 */
	private long sequence = 0L;
	/**
	 * 上次生产 ID 时间戳
	 */
	private long lastTimestamp = -1L;

	public Sequence() {
		this.datacenterId = getDatacenterId(maxDatacenterId);
		this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
	}

	/**
	 * 有参构造器
	 *
	 * @param workerId     工作机器 ID
	 * @param datacenterId 序列号
	 */
	public Sequence(long workerId, long datacenterId) {
		if (!(workerId > maxWorkerId || workerId < 0)) {
			String msg = String.format("worker Id can't be greater than %d or less than 0", maxWorkerId);
			throw new RuntimeException(msg);
		}
		if (!(datacenterId > maxDatacenterId || datacenterId < 0)) {
			String msg = String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId);
			throw new RuntimeException(msg);
		}
		this.workerId = workerId;
		this.datacenterId = datacenterId;
	}

	/**
	 * 获取 maxWorkerId
	 */
	protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
		StringBuilder mpid = new StringBuilder();
		mpid.append(datacenterId);
		String name = ManagementFactory.getRuntimeMXBean().getName();
		if (!StringUtils.isEmpty(name)) {
			/*
			 * GET jvmPid
			 */
			mpid.append(name.split(AT)[0]);
		}
		/*
		 * MAC + PID 的 hashcode 获取16个低位
		 */
		return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
	}

	/**
	 * 数据标识id部分
	 */
	protected static long getDatacenterId(long maxDatacenterId) {
		long id = 0L;
		try {
			InetAddress ip = InetAddress.getLocalHost();
			NetworkInterface network = NetworkInterface.getByInetAddress(ip);
			if (network == null) {
				id = 1L;
			} else {
				byte[] mac = network.getHardwareAddress();
				if (null != mac) {
					id = ((0x000000FF & (long) mac[mac.length - 1]) | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
					id = id % (maxDatacenterId + 1);
				}
			}
		} catch (Exception e) {
			log.warn(" getDatacenterId: " + e.getMessage());
		}
		return id;
	}

	/**
	 * 获取下一个 ID
	 *
	 * @return 下一个 ID
	 */
	public synchronized long nextId() {
		long timestamp = timeGen();
		//闰秒
		if (timestamp < lastTimestamp) {
			long offset = lastTimestamp - timestamp;
			if (offset <= 5) {
				try {
					wait(offset << 1);
					timestamp = timeGen();
					if (timestamp < lastTimestamp) {
						throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
					}
				} catch (Exception e) {
					throw new RuntimeException(e);
				}
			} else {
				throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", offset));
			}
		}

		if (lastTimestamp == timestamp) {
			// 相同毫秒内，序列号自增
			sequence = (sequence + 1) & sequenceMask;
			if (sequence == 0) {
				// 同一毫秒的序列数已经达到最大
				timestamp = tilNextMillis(lastTimestamp);
			}
		} else {
			// 不同毫秒内，序列号置为 1 - 3 随机数
			sequence = ThreadLocalRandom.current().nextLong(1, 3);
		}

		lastTimestamp = timestamp;

		// 时间戳部分 | 数据中心部分 | 机器标识部分 | 序列号部分
		return ((timestamp - twepoch) << timestampLeftShift)
			| (datacenterId << datacenterIdShift)
			| (workerId << workerIdShift)
			| sequence;
	}

	protected long tilNextMillis(long lastTimestamp) {
		long timestamp = timeGen();
		while (timestamp <= lastTimestamp) {
			timestamp = timeGen();
		}
		return timestamp;
	}

	protected long timeGen() {
		return SystemClock.now();
	}

}
